Choose active tool in Python
You can use the wm.tool_set_by_id() operator.



Example for a button:

layout.operator("wm.tool_set_by_id").name = "builtin.select_box"


Example operator:

import bpy


def main(context):
    bpy.ops.wm.tool_set_by_id(name = "builtin.move")
    for ob in context.scene.objects:
        print(ob)


class SimpleOperator(bpy.types.Operator):
    """Tooltip"""
    bl_idname = "object.simple_operator"
    bl_label = "Simple Object Operator"

    @classmethod
    def poll(cls, context):
        return context.active_object is not None

    def execute(self, context):
        main(context)
        return {'FINISHED'}


def register():
    bpy.utils.register_class(SimpleOperator)


def unregister():
    bpy.utils.unregister_class(SimpleOperator)


if __name__ == "__main__":
    register()